OSLO, April 20 (Reuters) - Norway's $1 trillion sovereign wealth fund, the world's largest, will back key proposals at the annual general meetings next week of three companies in which it holds stakes, the fund announced on Friday.

Norges Bank Investment Managament will vote in favour of a shareholder proposal on disclosure of water-related risks of Canada's Imperial Oil Limited, a proposal on climate change reporting at TransCanada Corp and to re-elect the board of Sweden's Boliden, it said.